The average human inhales more than two gallons of air per minute, over 2,900 gallons a day — that's about 145 times the amount of gas in the average car's tank. Depending on what is in that tank, a single car’s emission contribution affects the health of hundreds of people daily. Air pollution is more than just an environmental problem. It’s a major health risk that impacts both current and future generations.
Particulate matter, PM, is one type of air pollutant. These airborne particles are by-products of certain physical and chemical processes. Coarse particulates, PM10, have a diameter smaller than or equal to 10 microns. This is about the size of a grain of talcum powder. Fine particulates or PM2.5 are key indicators of significant air pollution and are equal to or smaller than 2.5 microns, which is the approximate thickness of spider web silk. PM10 generally causes upper respiratory issues, while fine particulates are small enough to get much deeper into the body.
Burning fuel, such as wood, releases black carbon, a particularly dangerous component of fine particulate matter that is made up of several forms of carbon. Certain oxygen compounds also cause concern. Nitrogen oxide, NO, and nitrogen dioxide, NO2, are transportation pollutants visibly present in urban areas. When combined, they create NOx, which is found near roadways. Ozone (O3) in the atmosphere protects against UV rays, but at ground level, it forms irritating smog. Finally, sulfur dioxide, SO2, comes from burning sulfur-rich fossil fuels, such as diesel.
Researchers have been studying the association between dry eye disease (DED) and air pollution for decades. Ophthalmologists suggest that symptoms such as photophobia and chronic pain are caused by the inflammatory immune response to air pollution. Research also shows that higher incidence of pollution-induced DED tends to occur in women, especially those with preexisting conditions, such as arthritis or thyroid diseases.
Air pollution affects both mother and fetus at all stages. Studies on mince show that PM2.5 particulates enter the mother’s bloodstream and negatively affect the supply of blood and nutrients to the placenta, leading to shorter gestation and offspring with low birth weights. Another study of pregnant women in Guangdong, one of China’s most polluted cities, shows that exposure to PM10 during the last trimester can lead to an 11-grambirth weight decrease [https://bmcpublichealth.biomedcentral.com/articles/10.1186/s12889-018-6307-7] for every 10 μg/m3 increase of PM10 levels.
The cocktail of airborne pollutants wreaks many types of havoc on the lungs. They damage cell RNA and DNA, creating oxidative stress that leaves the respiratory system at risk of irritation and swelling and causes wheezing, coughing, and shortness of breath. Children breathe mostly through their mouths, bypassing nasal filtration, and this makes them more vulnerable. Air pollution increases bouts of childhood pneumonia and other lower respiratory infections, leading to higher mortality rates, especially in developing countries.
Influenza-like illness or ILI is a generic name for the onset of fever, cough, and overall sickness that lasts about nine or 10 days. There are no known medications for ILI, unlike true influenza. Research points to an air pollution connection to both ILI and influenza. Studies show that SO2 contributes to some influenza cases, while PM2.5 is associated with both influenza and ILI emergency visits and hospitalizations. It turns out that air pollution suppresses regulatory T cells, lowering immune defenses.
Those who live in regions with air pollution can experience unexplained tiredness that they may pass off as stress or a poor night's sleep. According to doctors, PM and NO2 exposure can cause this fatigue. In addition to stress, the systemic inflammation caused by these substances decreases hemoglobin levels, leading to anemia and fatigue.
Traffic-related air pollution, TRAP, is related to poor development in children. Inhaling pollutants due to prolonged exposure damages the central nervous system, causing small vessel disease. One study showed that almost 57 percent of the Mexican children frequently exposed to PM2.5 had white matter lesions, compared to only eight percent of children living in less polluted areas. White matter helps messages pass from place to place, influencing cognition, a process hindered by these lesions.
The connection between respiratory inflammation and air pollution is significant, but extending the correlation to lung cancer is difficult. In a 27-year study of over 16,000 Norwegian men, scientists found that more than 20 percent developed lung cancer. The doctors made strong links between that diagnosis and more exposure to NOx at home due to increased vehicle emissions.
Not only does PM2.5 exposure increase infection risk and inflammation, but it can also raise arterial blood pressure, even with short-term exposure. Those who reside in regions with high levels of particulate matter may have more visits to emergency rooms due to overt hypertension. Additionally, high blood pressure related to more PM2.5 exposure heightens the risk of sudden cardiovascular events, such as stroke, because these particulates constrict blood vessels.
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